This project focuses on the cognitive processes underlying differences between healthy younger and older adults on neuropsychological tests of frontal lobe functioning. Previous research has shown substantial age-related declines on these tests, and there is strong evidence that changes in working memory ability may be important in explaining these declines. Working memory entails the capacity to simultaneously hold and process information about stimuli, responses, and goals needed to carry out a task. The primary hypothesis set forth here is that older adults have a reduced ability to update information in working memory. Thus, they may be less responsive to new input and fail to re-organize information already in working memory in response to new information. This research project includes a set of 17 experiments using three different neuropsychological tests of frontal lobe function: delayed response tests, self-ordered pointing tests, and tests of memory for temporal order. Specific experiments have three aims: (1) to determine whether changes in the ability to update working memory can explain age differences on these tests, (2) to identify which aspects of the updating process are most sensitive to aging; and (3) to rule out alternative explanations. Results of this research have applications for evaluating the psychological status of the elderly and designing optimal environments for them. The more immediate goal, however, is to advance our knowledge of the cognitive basis of normal aging.